A Study About Staining Of Complete Dentures In Endogenous Factors

ObjectivePatients with complete dentures not only care functional recovery such as chew and pronunciation, but also the appearance. The surface of complete dentures can be stained in3months, which not only affect the appearance, bring psychological barriers to the patients, also perplexes many dentists. The reasons of the staining and the solutions have become a major concern to dentists. In recent years, researchers mostly focus on the exogenous factors and the performance of the denture base material, such as dietary habits, the frequency of cleansing agents and the rough surface of denture base. Few researches are about the endogenous factors. Salivary as the external environment of the complete dentures in the mouth, soak and cover the dentures’surface constantly, has an important effect. In this study, the unstimulated whole salivary of patients was collected before denture insertion and after3months. The flow rate, pH value and the concentration of calcium, sodium, potassium, MG, sIgA in salivary were measured, to find out the effects of the unstimulated whole salivary on staining of complete dentures. MethodsIn this study, the unstimulated whole salivary of90patients was collected during September2009to April2011in Department of Prosthodontics, College of Stomatology, Tianjin Medical University. They don’t smoke and drink wine, tea or coffee. The complete dentures they all worn were made up of heat-curing denture base resins (poly methyl methyacrylate, PMMA) and Bayer artificial teeth. They use toothpaste and toothbrush to clean the complete dentures. According to the extent of staining, the samples were divided into mild, moderate and severe groups. The flow rate, pH value and the concentration of calcium, sodium, potassium, MG, slgA in salivary were measured before denture insertion and after3months. One-Way ANOVA and paired-samples T text were used for statistical analysis.Results(1)The flow rate, pH value, the concentration of SIgA and MG in mild group were higher than moderate and severe groups, the concentration of calcium, sodium and potassium were lower (P<0.01).(2)The flow rate after denture insertion (0.29±0.05ml/min) was significantly higher than before (0.25±0.07ml/min), pH value (6.48±0.22) was lower than before (6.71±0.18). There was an increase in the concentration of calcium, sodium and potassium (P<0.01).(3) The concentration of SIgA after denture insertion (51.57±5.64μg/ml) was significantly lower than before (62.83±6.01μg/ml), the concentration of MG after denture insertion (198.17±26.52μg/ml) was significantly lower than before (210.32±39.98μg/ml), P<0.01.ConclusionsThe lower the flow rate is, the more staining on complete dentures. Salivary flows constantly, micro-organisms don’t have enough time to reproduce. If the flow rate decreases, the mechanical cleaning ability and the buffering capacity will be weak, the number of adsorbed bacteria on the surface of complete dentures will be increase, and the staining will be more.The lower the pH value is, the more staining on complete dentures. The decrease of the pH value makes the salivary acidity enhanced, it will destroy the hydrophobic interface of the mucin and increase the bacterial adhesion. Mucin, as the specific bacterial metabolites, endogenous bacterial enzyme manufacturing degrades it, makes it to be the substrate of the metabolism of oral bacteria, ultimately converted to acid. Under these conditions, the acid-borne bacteria grow fast.The more the concentration of calcium is, the more staining on complete dentures. Calcium helps the glycoprotein adhesion to the denture surface, reduces the negative charge of the bacterial surface, weakens the repulsion of bacteria, and activates the glucan receptor of the bacterial cell surface to promote the formation of plaque, thereby staining more.The more the concentration of SIgA is, the more staining on complete dentures. SIgA can prevent the adhesion of bacteria and reduce the staining, the mechanism of action is:①Agglutinate the pathogenic micro-organisms, make them lost the adhesion capacity.②Combine with the micro-organisms, block the specific binding of the surface.③With the antigen of pathogenic micro-organisms, combine into antigen-antibody complex.The more the concentration of MG is, the more staining on complete dentures. MG is divided into MG Ⅰ and MG Ⅱ. MG I maintains the mucous membranes moist, reduces friction during mastication to prevent the invasion of pathogenic bacteria and potentially harmful substances as well as acid and protein hydrolase, thereby protects the oral tissues. MGⅡ contains a lot of neuraminidase, promotes the bacteria agglutination, conducive to remove bacteria from the mouth. The concentration of MG decreases, the bacterial clearance rates will be decrease, the staining will be worse.The insertion of complete denture, increases the flow rate, the concentration of calcium, potassium and sodium, and decreases the pH value and the concentration of SIgA and MG. After the complete denture insertion, patients chewing movement can stimulate the receptors of the masticatory muscles, temporomandibular joint and mucosal. It can also stimulate the salivary nucleus, causing the flow rate increased. The insertion of complete denture changes the oral microbial environment, increases the number of bacteria. The acid-borne bacteria uses the substrate to property acid, causing the pH value decreased. The bacteria can destroy the hydrophobic interface of the mucin, bacterial acid protease can decompose SIgA, eventually leads to the concentration of SIgA and MG decreased.